Poor on-time trends for Metro trains are costing riders time along the city’s most heavily-used transit route, and potentially leading some to consider other options for trips, a transit agency board member said Wednesday.

“I think we are losing ridership to this,” said Christof Spieler, during a Metropolitan Transit Authority committee meeting.

While no data indicates for certain that ridership is affected, Spieler said a handful of issues are hurting the reliability of trips on the Red Line, mostly as the line passes through downtown and Midtown. The primary cause is a problem with devices along the line which verify that the train is cleared to cross certain intersections.

Officials have been working for more than two years to find a fix to the axle counters, though its effect on the on-time performance of trains is worsening when coupled with traffic signal timing issues in downtown Houston. High heat and humidity also makes the problem worse, said Andy Skabowski, Metro’s chief operating officer.

The problem is longstanding, according to Metro’s monthly performance data. The last time Red Line trains finished a month with an on-time performance better than 95 percent – the benchmark Metro set for acceptable performance – was October 2013. In some months, fewer than 80 percent of trains arrived on time. Metro was unable to calculate on-time performance along the line for 10 months after a 5.3-mile extension of the line opened in December 2013.

Wednesday, Spieler called the recent on-time performance "abysmal."

The Green and Purple lines, which have more of the defective axle counters, have met their on-time performance mark of 85 percent since October, according to Metro reports. They have a lower on-time benchmark because they are just a year old and officials are still working on operational specifics. Trains on the Green and Purple line share the road with vehicle traffic as well, affecting their timing.

Often, a single problem along the line can stall numerous trains, Skabowski said. The goal is to have trains arrive at each station every six minutes most of the day. If a train is stopped by a faulty axle counter, the delay cascades as trains behind it are held up so they do not bunch together.

That can make the delays even more mystifying to riders, Skabowski said.

“What you’re seeing in front of you is not your train, it is two trains in front of you,” he told Spieler.

The axle counters were chosen by the builder of the Green and Purple lines, which opened last year after four years of construction. A potential fix is being tested now, and the early results are positive, Skabowski said. Siemens, the manufacturer, is resolving the issue at no cost to Metro.

But it comes at a cost to riders.

“It’s frustrating,” said James Hockley, 19. “You can see a train sitting there, and there’s nothing you can do.”

The train delays leave passengers waiting for trains at platforms. Even when they board, the delays keep them stopped at intersections for longer periods than necessary. The problem is even more noticeable because it is along a train line that carries more people than any other Metro service – roughly four times as many people as the most-used bus route and more than the agency’s entire park and ride system.

“It is the core of our system and it is not providing good service,” Spieler said.

MetroRail passengers stand on the platform waiting for a train in the Texas Medical Center on Friday, Jan. 22, 2016.

Photo: Brett Coomer, Houston Chronicle

City and transit officials, meanwhile, are still working to streamline traffic signal timing since the Green and Purple lines opened. To accommodate the trains and their effect on traffic, signals were retimed and the change is having various cascading effects on traffic, notably at peak commuting times.

Trains along Capitol and Rusk create a different pattern than conventional traffic, city officials have said, because of stops for picking up and dropping off passengers, and the time it takes to move from block to block and still give proper timing to pedestrians and cross-traffic. Vehicles turning right and stacking in front and behind the trains also affect timing, officials have said.